This invention relates generally to hammer mills, and more particularly pertains to the formation of the crushing surface from a series of adjacently arranged reversible grate bars that provide greatly extended usage of the apparatus.
Hammer mills and crushing machinery have long been utilized as the means for reducing the size of various types of ores, rock, and even what would generally have been considered as waste material in industrial operation such as metal turnings, and related by-products. As is well known, the principle of operation of such machinery is to rotatably dispose a plurality of hammers or the like within the structured machinery and to provide for their turning into close proximity with a reinforced surface to provide the impacting forces sufficient to cause breakage in the size of the material being treated. Obviously, the magnitude of the impacting force that is generated between the rotating hammer and the contiguous crushing surface can be quite enormous thereby requiring that not only must the hammers be constructed of high strength materials, but that the crushing surface itself must be able to withstand the impact of equivalent pressures. Furthermore, the continuous impingement of the hammers against materials lying on the crushing surface causes significant friction that eventually through wear, if not fracture, deteriorates the condition of the crushing surface to the extent that the setting of the hammers with respect to the surface become increased thereby causing disparity in the size of the crushed material desired to be acquired from the apparatus.
To overcome the foregoing type of problem, either a new crushing surface must periodically be installed into the apparatus, replacing the old and worn one, or the surface itself must be reversed in its positioning so as to expose a new surface thereby attaining a double advantage from a single surface structure. This feature of attaining at least two operative surfaces from the crushing surface of such machinery is not new, and as can be seen from the United States patent to Anderson, U.S. Pat. No. 1,746,512, reversible type screen bars were shown for forming the screen of the disclosed crushing machinery. As can be seen, the individual narrow bars extend between the supporting portions of the crusher, having their end projections extending within said portions for support. While there is usefulness in being able to reverse the screen bar of the type shown, one drawback is that the shown bars do not have any substantial width due to the fact that the end projections had to be of a narrowing width to provide for their accommodation within the curved supporting portions of the shown cage. As a result, the strength of such bars was significantly reduced, and the bars would succumb to frequent fracture when exposed to the impacting forces of the heavy rotating type of hammers as indicated.
Efforts have been made to rectify the problems associated with the utilization of the narrow type of screens or bars as previously shown in the prior art, and the United States patent to Williams, U.S. Pat. No. 3,465,973, discloses a wider and more structurally sound type of cage bar that contains the advantages of being reversible, and which mounts to supporting structure provided along each end wall. As can be seen from this particular invention, one problem with its operating ability is in the style of mounts used to support the bar at its ends. As shown, various styles of abutment means, wedging elements, liners, and bolts are required to furnish stable support for the depicted cage bar in place. While such mounting structure may be theoretically useful for its intended purpose, in practice, the tremendous forces of impact caused by the rotating hammers when encountering the treated materials exert pressure against such piecemeal assembled type of mounting structure, which forces can either cause fracture to its various components, or at least, due to its jarring impact, cause their loosening, with the concurrent looseness of the cage bar itself in its position within the crusher surface.
To overcome the problems encountered with the utilization of multi-component mounts for holding crusher bars within its formed surface, the herein disclosed invention utilizes a single mounting means in the form of a shoe, one of each which cooperates with the ends of the grate bar, for providing its stable support between the side walls of a hammer mill. The use of such support was given some consideration in the past, not for use in support of reversible grate bars, but rather, and as shown in the United States patent to Bonarrigo, U.S. Pat. No. 3,617,007, for application in holding upper and lower grate sections together, with the upper section interlocking within a lower supporting section. Then, as its upper grate wears out, it must be replaced in the assembly. The most apparent problems associated with this style of grate bar assembly would appear to be twofold, one that it requires a new cast upper grate section each time such a bar is to be replaced, and secondly, the style of support as is provided through its lower grate section is not designed for accommodating a reversible style of grate bar.
In view of the foregoing, it is the principal object of the present invention to provide reversible grate bars for use in the assembly of a surface for a crusher and which are stably mounted into such a configuration through the use of a minimum of supporting components.
A further object of this invention is to provide a reversible grate bar with accompanying end shoes that are complemental in formation so as to provide for their stable and abutting support when assembled into the formation of a crushing surface.
A further object of this invention is to provide a structurally formed grate bar and its supportive end shoes that are properly contoured so as to provide for their mating relationship into a contiguous relationship when assembled into the formation of a crusher surface.
A further object of this invention is to provide a grate bar which is reversible and is supported at each end within a hammer mill through the use of a single structural member.
An additional object of this invention is the provision of a grate bar that is so contoured as to provide for its tight retention intermediate the end supports of a hammer mill.
These and other objects will become more apparent to those skilled in the art upon reviewing the summary of this invention and in view of the description of its preferred embodiment when read in light of its drawings.